1. Field of the Invention
The present invention relates to a stationary original type image reader and particularly to a support structure for supporting reflectors on a half rate carriage that moves by half of the moving distance of a light source lamp for keeping an optical path length constant from the image-formed surface of the original to an image-processing part of the image reader.
2. Description of the Related Art
FIG. 4 is a schematic diagram illustrating the configuration of a conventional stationary original type image reader, such as one disclosed in Japanese Patent Laid-Open Publication No. Hei. 9-331425 (1997), to read image data from an original on a platen glass. As shown in the figure, an image reader 1, such as a copying machine or a scanner, is provided to read image data of an original (e.g., a paper document) or the like placed on a platen glass 9 to subject the image data to various kinds of processing. The image reader 1 utilizes movable carriages 3 and 4 for scanning the original. Carriage 3 includes light source lamps 5 for irradiating the original with light beams and a reflector 10 mounted thereon. Carriage 4 includes reflectors 11 and 12 mounted thereon. These reflectors 10, 11, 12 form an optical path for guiding the desired image data from the original to an image-processing part 7 such as a CCD (Charge-Coupled Device). Therefore, the image formed on the original can be scanned by moving the carriages 3 and 4 along the original to pick up the image information from the original.
In other words, the optical path length from the image-formed surface of the original to the image-processing part 7 must be kept at a constant length even though each of the carriages 3 and 4 moves. Therefore, as described above, the image reader 1 has a combined structure of the full rate carriage 3 and the half rate carriage 4. Typically, the half rate carriage 4 is moveable by half of the moving distance of the full rate carriage 3. More specifically, as described above, the first reflector 10 for receiving the image from the original is mounted on the full rate carriage 3. The second reflector 12 for receiving the reflected image from the first reflector 10 and the third reflector 13 for receiving the reflected image from the second reflector 12 are mounted on the half rate carriage 4, respectively. The reflected image from the third reflector 13 is then incident on the image-processing element 7.
Each of the carriages 3 and 4 is arranged so as to move in parallel with the image-formed surface of the original. It means that an optical path 8 between the carriages 3 and 4 should be also in parallel with the image-formed surface of the original and in a direction along which each of the carriages 3 and 4 moves. Therefore, the first reflector 10 is arranged at an angle of 45° with respect to the platen glass 9.
As shown in FIG. 5, the reflected light beams from the first reflector 10 is transmitted to the second reflector 11 along the optical path 8. Then, the second reflector reflects the light beams to the third reflector 12. Subsequently, the reflected light beams from the third reflector 12 travels in the direction parallel to the optical path 8. In this case, furthermore, the support structure of each of the second and third reflectors 11 and 12 on the above half rate carriage 4 is constructed such that the second reflector 11 and the third reflector 12 form a right angle (i.e., 90°), while the second reflector 11 is arranged at an angle of 45° with respect to the optical path 8 of the reflected light beams from the first reflector 10.
Furthermore, each of the full rate and half rate carriages 3 and 4 moves as wire 14 (FIG. 4) moves. That is, carriages 3 and 4 are engaged on the wire 14 which is wound up around a pulley 15 by the driving force of a motor (not shown). The movement of such a wire 14 is guided with pulleys 16 and 18. As indicated by the double-dashed line in FIG. 5, carriages 3 and 4 are overlapped on one another in part when the full rate carriage 3 moves to the fullest extent in the direction toward the half rate carriage 4. In this case, the carriages 3 and 4 are able to come closer to one another as far as the first and second reflectors 10, 11 come into contact with one another.
However, it is difficult to sufficiently overlay the full rate carriage 3 and the half rate carriage 4 when these carriages 3 and 4 come into contact with one another. As described above, the reason is that the support structure of each reflector 11 and 12 on the above half rate carriage 4 is constructed such that the second and the third reflectors 11 and 12 are arranged at 90° with respect to one another and the second reflector 11 is arranged at an angle of 45° with respect to the optical path 8 of the reflected light beams from the first reflector 10. In other words, there is a comparatively large space under the first reflector 10 of the full rate carriage 3. When these carriages 3 and 4 come into contact with one another to bring the first and second mirrors 10 and 11 closer, such a space can be formed between the first reflector 10 of the full rate carriage 3 and the third reflector 12 of the half rate carriage 4.
It would be desirable to provide a support structure of each reflector on the half rate carriage that allows the full rate carriage 3 to slide into the half rate carriage 4 so as to make them closer by the distance of such a space.